1. Field of the Invention
This invention relates to a recording device and a reproducing device. More particularly, the present invention relates to a recording device by use of a recording medium having a layer structure of an organic compound between a pair of electrodes one of which is made a probe electrode, and exhibiting memory effect for the switching characteristic of voltage and current, and also to a device for reproducing the information recorded on the recording medium.
2. Related Background Art
In recent years, uses of memory materials form the nucleus of electronics industries such as computers and their related instruments, video discs, digital audio discs, etc. and developments of their materials are also under active progress. The performances demanded for memory materials may differ depending on uses, but may generally include:
(1) high density and large recording capacity; PA1 (2) rapid response speed of recording and reproduction; PA1 (3) small power consumption; PA1 (4) high productivity and low cost; etc.
Heretofore, semiconductor memories or magnetic memories employing magnetic material or semiconductor as the base material have been predominant, but with the advancement of laser technique, inexpensive and high density recording media with optical memory by use of an organic thin film such as organic dye, photopolymer, etc. are now emerging in the field of art.
On the other hand, recently, a scanning type tunnel microscope (hereinafter abbreviated as STM) capable of observing directly the electron structure of the surface atoms of a conductor has been developed [G. Binning et al, Helveica Physlca Cata, 55, 726 (1982)], and it has become possible to measure both single crystalline and amorphous materials with high resolving power of real space image. Besides, it has the advantage that observation can be made at low power without giving damage by current to the medium. Further, it can be actuated in air and applied to various materials, and therefore a broad scope of applications is expected.
STM is based on the phenomenon that tunnel current flows when the probe and an electroconductive substance were made to approach to a distance of about 1 nm with a voltage applied therebetween. This current is very sensitive to the distance change between the both, and by scanning the probe so that the tunnel current may be maintained to be constant, the surface structure of the real space can be drawn and at the same time a variety of information about the total electron cloud of the surface atoms can be read. Although analysis by use of STM is limited to electroconductive samples, it is becoming to be introduced to structural analysis of a monomolecular film very thinly formed on the surface of an electroconductive material, and application as the reproduction technique of high density record by utilizing the difference in the state of individual organic molecules may be also considered.
On the other hand, in the prior art, the method of forming a latent image by discharging or current supply by use of a needle-like electrode has been known as the electrostatic recording method, and a large number of applications for recording paper, etc. have been made (Japanese Laid-open Patent Publication No. 3435/1974).
The film thickness used for this electrostatic recording medium is order of microns, and there has been no report about an example in which the latent image on said medium is electrically read and reproduced.
Also, proposal of a molecular electronic device having imparted to one organic molecule the function of a logic element or memory element, etc. has been presented, and studies about the Langumuir-Blodgett film (hereinafter abbreviated as LB film) which may be regarded as one of the construction technique of molecular electronic device have been actively done. An LB film has laminated organic molecules regularly one molecular layer by one molecular layer, and the film thickness can be controlled in a unit of molecular length, whereby uniform and homogeneous ultra-thin film can be formed. As preparation of the device by making full avail of this specific feature, many attempts have been made to use an LB film as the insulating film. For example, there are tunnel junction element with a metal-insulator-metal (MIM) structure [G. L. Larkins et al, Thin Solid Films, 99, (1983)], an electroluminescent element with a metal-insulator-semiconductor (MIS) structure [G. G. Roberts et al, Electronics Letters, 20, 489 (1984)] or a switching element [N. J. Thomas et al, Electronics Letters, 20, 838 (1984)]. According to these series of studies, the element characteristics have been investigated, but the there still remain unsolved problems that reproducibility and stability are lacking, such as variance or change with lapse of time in characteristics in respective elements, etc.
In the prior art, the above investigations have been made primarily about LB films of fatty acid which can be handled with relative ease. However, from organic materials which has been deemed to be inferior in heat resistance and mechanical strength, there are being developed heat-resistant and mechanically stronger organic materials one after another. We have studied intensively in order to prepare a MIM element excellent in reproducibility and stability by using an LB film by use of these materials as the insulator, and consequently could successfully prepare a thin and uniform dye insulating film not found in the prior art. Also, as a consequence, a MIM element capable of exhibiting the switching phenomenon having an entirely novel memory function has been discovered.